Many diverse systems use a pump to pull a fluid (e.g., water) through a suction passageway (typically including a nozzle) in order to drive a turbine. In designing such a system, it is desirable that the passageway define a flow area sufficiently small to produce a fluid velocity sufficiently high to efficiently drive the turbine. However, a relatively small flow area constitutes a flow restriction which, potentially, can obstruct objects (e.g., debris) borne by the fluid. To avoid obstructing the passageway, it would, of course, be preferable that the flow area be as large as possible. These competing design requirements, i.e., (1) reducing flow area to increase fluid velocity and (2) increasing flow area to reduce the potential of flow obstructions, are generally compromised in the design process.
Various efforts intended to mitigate the aforementioned competing requirements are discussed in the prior art. For example, U.S. Pat. No. 4,656,683 describes a suction cleaner for swimming pools in which the suction “nozzle is made of silicone rubber so that it can distend to allow large objects to pass through”.
U.S. Pat. No. 5,604,950 describes an anti-clogging variable throat suction cleaning device intended to overcome the disadvantages and shortcomings of the prior art including aforementioned U.S. Pat. No. 4,656,683. More particularly, U.S. Pat. No. 5,604,950 describes a suction nozzle including at least one body portion which is moveable relative to another body portion for the purpose of enabling the throat to expand in response to the relative movement of the body portions. The patent asserts that “The resulting expansion of the suction nozzle allows substantially unrestricted passage of large foreign objects through the throat during the operation of the cleaner”.